Oct i^. 1921 Aecial Stage of the Orange Leaf rust of Wheat 165 



spores about 13 ju in diameter. The Sydows {23, p. 718-719) give the 

 measurement of the aeciospores as 13 to 18 /x in diameter or 13 to 16 by 

 18 to 20 M and note that no swelHngs are produced on the leaves of the host. 

 An examination of Eriksson's Fungi Parasitici Scandinavici 432a, col- 

 lected by Juel in Norway, gives the following measurements: Peridial 

 cells, 16 to 19 by 19 to 29 /x; the outer wall, 10 /x; the inner, 3 to 4 ju; 

 aeciospores 14 to 16 by 16 to 21 m- 



Rostrup (22, p. 269-273), in Denmark, obtained infection with aecio- 

 spores from Thalictrum minus on Elymus arenarius and considered the 

 rust to be Puccinia Elymi Westendorp. The writers have seen neither 

 description nor material of these aecia. 



The Sydows (23, p. 827) mention that Lindroth in Finland connected 

 an aecidium on Thalictrum m/ijus with a rust on Agropyron caninum. 

 No description or material of this connection is available for study. 



In North America a number of connections have been established by 

 the cultures of Arthur and of Fraser. Arthur (/, v, i, p. 248-249) reports 

 culturing a rust found associated with aecia on Thalictrum sparsifiorum 

 from Bromus Porteri to T. dioicum. To this he gave the name Puccinia 

 alternans. He describes the aecia as having peridial cells 2 1 to 29 /x long 

 with the outer wall 9 to 12 /x thick and the inner 5 to 7 /x and with aecio- 

 spores 15 to 20 by 17 to 24 IX. A number of other species of Thalictrum 

 are given as hosts. 



Arthur (j, v. 2, p. 226) also reports obtaining infection from telia on 

 Agropyron resulting in aecia on Thalictrum alpinum but not on T. dioicum. 

 This material he considered as belonging in Puccinia obliterata Arth., 

 which he had previously shown as having aecia on Aquilegia. A study 

 of the material obtained by this culture shows little or no hypertrophy 

 of the host tissue. The peridial cells measure 16 to 21 by 24 to 32 /x, 

 having the outer wall 7 to 9 ^u thick and the inner 3 to 5 /x. The aecio- 

 spores measure 14 to 18 by 18 to 23 jx. 



Still another connection was obtained by Arthur (i, v. 8, p. 132-133) 

 when he cultured a rust on Festuca Thurberi to Thalictrum dioicum, 

 producing aecia. To this he later (2, p. 113) gave the name Puccinia 

 Cockerelliana Bethel. He gives the peridial cells as 16 to 23 by 27 to 

 36 /x with the outer wall 6 to 8 /x and the inner 2 to 3 a« and aeciospores 18 

 to 24 by 20 to 29 IX with a wall 1.5 to 2.5 ix thick. The natural host for the 

 aecia is given as T. Fendleri. 



Fraser {14, p. 131-133) reports sowing aeciospores from Thalictrum 

 dasycarpwn on Elymus canadensis, E. virginicus, Agropyron tenerum, 

 A. Richardsonii, Hordeum jubatum, Triticum vulgare, and Bromus 

 ciliatus, obtaining infection on E. canadensis, E. virginicus, H. juba- 

 tum, and B. ciliatus. When, however, the rust obtained upon B. cili- 

 atus was sown on E. virginicus, A. tenerum., A. Smithii, A. repens, and 

 H. jubatum no infection was obtained on these species. From these 

 results Fraser concludes that two strains of Puccinia Agropyri KHis and E., 



